Electromagnetic horn



Original Filed July 10 Patented May 20, 1930 uru'riu) STATES PATENT OFFICE FARNU'M DORSEY, OF ROCHESTER, NEW YORK, ASSIGNOR, BY MESNE ASSIGNMENTS,

TO NORTH EAST APPLIANCE CORPORATION,

PORATION OF NEW YORK OF ROCHESTER, NEW YORK, A COR- ELECTROMAGNETIC HORN Original application filed July 10, 1925, Serial No. 42,760. Divided and this application filed April 2,

. 1926. Serial No. 99,290.

. This invention relates to horns or soundproducing devices, such as are widely used upon motor vehicles, of the type in which a sonorous diaphragm is actuated by an electromagnet energized by anintermittent current.

In horns of the kind in question it is usual to provide a circuit-breaker by which the flow of current through the magnet is interrupted periodically, the circuit-breaker being actuated by connection with the diaphragm or with some other member vibrating in harmony therewith, and the object of the present invention is to provide an improved circuitbreaker for this purpose, together with simple and convenient means for supporting the circuit-breaker within the shell or body of the horn, and for adjusting the circuitbreaker to compensate for wear and to secure a correct tone. Tothe foregoing end, the invention consists in the circuit-breaker hereinafter described, in itself and in combination with the other horn elements associated therewith, as defined in the annexed claims.

This application is a division from my pending application Serial No. 42,7 60, filed July 10, 1925, Patent No. 1,750,348, March 11, 1930.

In the accompanying drawings, Fig. 1 is a plan view, partly in section, of an electromagnetic horn embodying the present invention. Fig. 2 is a fragmentary side elevation, partly in section approximately on the line 2-2 in Fig. 3. Fig. 3 is a partial front olevation of the horn, with the front plate and diaphragm removed, including the rear shell or housing and the parts attached thereto and enclosed therein. Fig. 4 is a bottom view partly in section, of the circuit breaker and the parts immediately associated therewith.

Fig. 5 is a front elevation of the circuitbreaker, with the front insulation removed.

' Fig. 6 is a sectional view of the circuitbreaker, on an enlarged scale; and Fig. 7 is a detail view showingf in perspective, the

circuit-breaker associated with the base member on which it is supported.

The invention is illustrated as embodied in a horn having an elastic metal diaphragm 5, which is gripped and supported, at its margin,.,between a front plate 6 and a cupshaped metal shell or housing 7. Attached to the front plate 6 is a horn-proper or projector 8, which may vary in length according to the pitch of the note which it is desired to produce. The front plate and the housing are secured together by bolts 9.

The electromagnet comprises a central core 10, which is surrounded by a coil or winding 11. It comprises, also, a generally U-shaped yoke 12 formed of a relatively wide and thin strip of steel, with its extremities bent inwardly, as shown in Fig. 1. The core and the yoke are fixed rigidly to the rear wall of the housing.

The armature 15, which cooperates with the electromagnet, has the general form of a relatively wide and long bar, secured to the middle of the diaphragm by a bolt 16. The bolt is made of steel, so that its head 18, lying at the rear of the armature, constitutes a part of the magnetic circuit, cooperating with the core 10. The circuit is completed through the armature and through the lateralmembers of the yoke, the magnet thus having three poles, all separated by suitable air-gaps from the armature.

The circuit-breaker comprises a normally stationary contact 20, and a movable contact 21 cooperating therewith. The movable contact is mounted on a blade spring 22, and this spring projects, at one extremity, into the path of movement of the armature, so that at each rearward vibration of the latter the spring is engaged and pressed "rearwardly," thus separating the contacts. Where it is desired to insulate both sides of the circuit from the casing of the horn, a piece of insulating material 23 is attached to the end of the blade-spring to prevent direct metallic engagenient between the armature and the s rin In order that the circuit-breaker may be conveniently adjusted to regulate thecurrent impulses in the magnet, the contact 20 and the blade-spring 22 are mounted upon, but insulated from, a support in the form of. a sheet-metal plate 24. The plate is bent rear- .wardly at its lateral edges, so .as to provide parallel arms 25, continuous with flanges 32.

ends against the At its rearedge the plate has two rearward projections 26, which rest against the inner surface of the housing as shown in Fig. 3. The plate cooperates with a base-member, formed also of sheet-metal and comprising a horizontal portion 27 and a vertical portion 28 (referring to Fig. 2). Two lugs 41, projecting from the horizontal portion, are riveted to the housing to secure the base in place. The horizontal portion is cut away at its forward end. as shown particularly in Figs. 2 and 4, and formed with lugs 29 which overhang the projections 26 on the plate 24. Through the reaction of the springs and other parts hereinafter described, the projections 26 are held constantly in the position described, so that the lugs 29 act as pivotal bearings about which the plate 24 may swing on a line adjacent the inner surface of the housing, and in the general direction of movement of the diaphragm and the armature.

At its inner extremity the part 28 of the base is provided with two forwardly bent projections 30, which constitute supports for coiled springs 31, ressing at their forward anges 32 on the plate 24. The arms 25 rest against the bar 33 into which an adjusting screw 34 is threaded, and this screw projects through an opening in the wall of the housing, so that it is accessible from the outside and may be turned by a screw-driven The bar 33' is of a length to extend laterally from the screw 34 so as to project beyond the arms 25 as shown in Fig. 4, and rides along the plate 28 between the projections 30 on the one hand and the arms 25. Thus a guideway is formed for the cross-bar, and the same is prevented from turning uponamovement of the adjusting screw 34. The springs 31 tend normally to rock the plate 24 in a forward direction, so as to cause the contactsto be separated earlier in each rearward motion of the armature.

. This tendency of the springs is resisted, howover, by the arms, the cross-bar and the adjusting screw; and by rotation of the latter the operative position of the circuit-breaker may thus be exactly determined, while the constant pressure of the springs 31 not only prevents any accidental movement, but also acts to'thrust the projections'26 outwardly and hold them in effective engagement with the housing and with the lugs 29.

In circuit-breakers previously employed in horns of this type, it has been customary to provide adjustment at two points in the circuit-breaker, in order that the effective spring-tension by which the contacts are held together may be kept constant, notwithstandmg adjustment of the time of operation of the circuit-breaker. In the present construction, in which the circuit-breaker as a whole is moved in'the direction of motion of the armature, the necessity of this double adj ustment is eliminated, since the spring-pressure between the contacts remains unaffected by any movement of the adjusting screw.

To render the blade-spring of the circuitbreaker durable and eflicient, it is necessary to give it suflicient length to prevent overstraining of the material, andthis is diflicult in. the restricted space available. In the illustrated construction this difiiculty has been solved by making the spring U-shaped in general form, attaching the shorter arm 36 of the spring to the front 'of the plate 24, so that the spring bends around the outer edge of the plate and its longer arm extends on the opposite side thereof, and beyond the lower or inner edgeof theplate, as shown.

The blade spring, the stationary contact,

and the terminals by which they are connected with other parts of the instrument,

are secured to the plate 24 by means of screws 37. The fixed contact 20 is mounted on a plate 40, and this plate and the stationary end 36 of the spring 22 areclamped between two plates of insulating material, 38 and 39..

Metal terminal strips 42 lie in contact with the two contact-supporting members, and

serve for the convenient connection of the wires by which the circuit-breaker isconnected Wltllt-llG electric circuit.

An additional advantage of the illustrated construction of the circuit-breaker resides in the fact that it may be readily removed from the housing,when desirable, without disconnecting any attaching device. For this purpose it is necessary merely to back ofl the adjusting screw until the bar 33 has been pressed forwardly into engagement with the spring supports 30. If then the inner end of the circuit-breaker be pressed rearwardly, the projections 26 will be withdrawn from engagement with the lugs 29, whereupon the circuit-breaker is freed from connection with the other parts, except through the wires.

Owing to the pressure of the springs 31.

vent accidental rotation of the screw from the position to which it has been adjusted.

This friction is enhanced by the conical form 1 of the screw-head cooperating with a socket of corresponding form, as shown The invention claimed is:

1. In an electromagnetic horn, the combination'of a vibratory assembly, including a diaphragm and an armature mounted on the rear thereof; a housing supporting-the diaphragm; an electromagnet cooperative with the armature and mounted upon the housing;

a plate lying substantially parallel with the diaphragm, means pivotally supporting said plate, adjacent the wall of the housing, at one side of the armature, a stationary contact and a spring-blade fixed on said plate, said springblade carrying a movable contact and projecting into position to be actuated by a part of the vibratory assembly near the center. thereof; arms projecting rearwardly from the plate; a cross-bar engaging said arms; means biasing said arms toward the cross-bar; and

means accessible from the outside of the housing for adjusting the. position of the cross prises a spring cooperating with the plate to move said plate on its pivot in one direction in opposition to the action of the adjusting screw.

3. An electromagnetic horn, as defined in claim 1, provided-With a member which is attached to the housing on the inside, means on said member constituting said pivotal supporting means for said plate, a guideway for the cross bar and two spring supports; and

two springs constituting the biasin means resting on said supports and engaging said plateto maintain constant tension in the adjusting mechanism. C 4. In an electromagnetichorn, the combination, with an electromagnet, and a vibratory assembly including an armature actuated by the magnet, of means for breaking the circuit of the magnet, comprising a U-shaped blade-spring with one arm longer than the other; a plate, to one side of which the shorter arm. of the blade-spring is attached, the spring curving around one end of the plate and the longer arm lying on the other side of 40 the'plate and projecting beyond the other end thereof and lying in position to be ac tuated by engagement with a part of said vibratory. assembly; cooperative contacts mounted, respectively, on the plate and on the'blade-spring; and means for moving the plate in the general direction of movement of the vibratory assembly, to adjust the operation ofthe circuit-breaker.

-5. In an electromagnetic horn, the combina- \9 tion with a vibratory assembly comprising a diaphragm and an armature, a housing supporting the diaphragm and enclosing the armature, and an electromagnet cooperating with the armature, of a circuit-breaker com- U5 prising: a blade-spring carrying a movable contact and supported, at its outer end, by

connection with the housing, the blade-spring projecting inwardly toward the axis of the diaphragm, with its inner end lying in the E9 path of movement of the armature, a fixed contact cooperating with the movable contact,'and a normally stationary support, for the fixed contact, means adjustably mounting it to adjust the position of the stationary contact, said means passing througha wall of said housin so as to be outside thereo I 6. An electromagnetic horn,as defined in claim 5, in which said adjusting means is a screw-threaded member having a head which abuts against the wall of the housing,thesupport for the fixed contact being provided with spring-means tending to move it in one irection and to maintain constant frictional engagement between said head and the housing to resist-accidental rotation of the ad- 2. An electromagnetic horn, as defined in r 15 claim 1, in which said biasing means comjusting means.

nation, with an electromagnet, and a vibratory assembly including an armature actuated by the magnet, of means, for controlling the circuit of the magnet, comprising: two cooperative contacts, one stationary and the other movable, the stationary contact being fixed on a plate and the movable contact on one arm of a U-shaped blade-spring, a support to which the other arm of the bladespring is fixed but from which it is insulated, said plate being also fixed to but insulated from said support; the free arm of thebladespring projecting across and beyond the fixed contact and into position to be engaged and actuated bya part of the vibratory assembly, and means swingingly mounting said support so that it may be moved to adjust the operative position of the blade spring.

FAl tNUM F. DORSEY.

the support on the housing; and adjusting 5 means, engaging said support, for moving accessible from the 7. In an electromagnetic horn, the combi- 

